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Optical Engineering

Application of extended tuning range for external cavity diode lasers to water vapor differential absorption measurements
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Paper Abstract

Recent advances using electronic feedback to control the optical cavity length of external cavity diode lasers (ECDLs) have led to extended continuous tuning ranges. Mode-hop-free tuning over more than 65 GHz has been demonstrated. The ability to tune ECDLs asross a wide range is particularly useful to differential absorption lidar (DIAL) systems that use ECDLs as seed laser sources. Experiments using a multiple-pass gas absorption cell are performed to test a widely tunable, amplified ECDL DIAL transmitter with this extended tuning range system. Experimental results show that the system can be tuned to and maintained at a user-defined wavelength for one hour, then tuned to and maintained at a second user-defined wavelength for one hour without mode hopping. This tuning is successfully accomplished between wavelengths separated by approximately 44 GHz. A computer-controlled feedback loop in the tuning system tunes and holds the laser system to the on- and off-line wavelengths to within ±88 MHz. The laser power transmitted through the gas absorption cell is monitored and used to perform a differential absorption calculation to find the number density of water vapor molecules within the cell. The measured value is in agreement with a HiTRAN prediction of the expected value.

Paper Details

Date Published: 1 August 2007
PDF: 7 pages
Opt. Eng. 46(8) 084301 doi: 10.1117/1.2771654
Published in: Optical Engineering Volume 46, Issue 8
Show Author Affiliations
Michael D. Obland, Montana State Univ./Bozeman (United States)
Amin R. Nehrir, Montana State Univ./Bozeman (United States)
Kevin S. Repasky, Montana State Univ./Bozeman (United States)
John L. Carlsten, Montana State Univ./Bozeman (United States)
Joseph A. Shaw, Montana State Univ./Bozeman (United States)

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